Device for ensuring the automatic return of a servo-motor to its extreme position inthe event of failure of the hydraulic supply



Aug. 31, 1965 R. LUCIEN 3,203,183

DEVICE FOR ENSURING THE AUTOMATIC RETURN OF A SERVO-MOTOR TO ITS EXTREME POSITION IN THE EVENT OF FAILURE OF THE HYDRAULIC SUPPLY Filed Jan. 29, 1964 2 Sheets-Sheet 1 FIG/l Aug. 31, 1965 R. LUCIEN 3,203,183

DEVICE FOR ENSURING THE AUTOMATIC RETURN OF A SERVO-MOTOR TO ITS EXTREME POSITION IN THE EVENT OF FAILURE OF THE HYDRAULIC SUPPLY Filed Jan. 29, 1964 2 Sheets-Sheet 2 FIGE United States Patent 3,203,183 DEVK'JE FUR ENSURING THE AUTOMATIC RE- TURN OF A SERVG-MQTOR TO ITS EXTREME PGSITIGN IN THE EVENT OF FAILURE OF THE HYDRAULIC SUPPLY Reu Lucien, Neuilly-sur-Seine, France, assignor to Societe a Responsabilite Lirnitce Recherches Etudes Production REE, Paris, France, a corporation of France Filed Jan. 29, 1964, Ser. No. 341,042 Claims priority, application France, Feb. 2, 1963, 923,548, Patent 1,355,040 Claims. (Cl. 6tl51) The invention relates to a device which is adapted for automatically ensuring the return of a jack of an electrohydraulic servo-motor to its extreme position, in the event of a power failure.

The resetting of the device is automatically effected as soon as operation is restored.

According to the invention, the return to the extreme position in the case of lack of power is ensured by an accumulator connected on one of the circuits of a pump and which, in a set position, is held hydraulically locked by means of the pressure of fluid in the other circuit. A stoppage of the pump causes a drop in pressure in this second circuit and ensures the release of a movable element of the accumulator and discharge of the accumulator into the corresponding chamber of the jack.

The invention will be described with reference to the accompanying drawings, which are given by way of examples and without any limitative sense.

In the drawings:

PEG. 1 is a diagrammatic sectional view of a first embodiment of my invention, and

FIG. 2 is a diagrammatic sectional view of a second embodiment of my invention.

These two figures relate to two embodiments of the invention directed to the positioning device with electrohydraulic operation, as described in US. patent application No. 109,059, filed on May th 1961, and now abandoned, by the same applicant, the operation of which will be briefiy described hereinafter since these two applications differ from each other in the locking of the hydraulic accumulator.

In accordance with FIG. 1 or FIG. 2, a pump 1 connects with two separate and identical supply conduits 2 and 3 and discharges through two orifices 4 and 5 which are closed to a greater or less extent by the working face 6 of a flat side valve or distributor valve '7 of the distributor D. Each of the conduits 2 and 3 is in communication with a chamber 3 and 9 of a jack. Any displacement of the face 6 causes a variation of pressure in the two circuits or conduit 2 and 3, and therefore in the two chambers 8 and 9 of the jack, which results in displacement of the piston 10 of the jack. The operation of the slide-valve 7 is effected by the movements of a balance 11 which is continuously subjected to the oppositelyacting forces of a magnetic motor 12 and a counterreaction spring 13, the other extremity of which is connected to the piston 10 of the jack. Each of the chambers 8 and 9 of the jack is provided with an over-pressure valve 14 and 15.

According to the invention, an accumulator of the spring type or of the oleo-pneumatic type, is connected in parallel with the circuit 2 of the pump 1 of the servomotor. In order to prevent the accumulator 20 from emptying itself through the orifice 4 when tripped, a controlled valve 21 is placed on the upstream side of the orifice 4 and is held open by the action of the pressure of the fluid in the circuit 3 on its operating piston 22. In the application of the invention according to FIG. 1,

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the fluid pressure of the circuit 3 holds the accumulator 20 locked in a fully charged or set position by pressurized fluid acting on a piston 23, co-operating with a crank lever 24, in which slides a stud 25 on a rod 26 of the accumulator 26.

A slidable valve 27 has a double function; an orifice 2? in an otherwise closed end wall of slidable valve 27 causes a loss of pressure in the circuit 3, which ensures the operation of the two pistons 22 and 23, and during the stoppage of the pump 1 it enables the circuit 3 to be rapidly exhausted to tank through the orifice 29. Finally, a valve 36 enables exhaust of the circuit 3 to tank when the pump is restarted and the accumulator 20 is being reset. The closure of valve is effected by the rod 25 of the accumulator 20 itself, at the end of the setting operation of the accumulator.

The device in accordance with FIG. 1 operates in the following manner: the stoppage of the pump 1 initiates the following sequence:

Movement of the valve 27 to the left in FIGURE 1 to a position in which circuit 3 is exhausted to tank through orifices 28 and 29.

Closure of the valve 21 and retraction of piston 23 by its spring 31, thus releasing the locking means which held the accumulator in its fully charged position.

The accumulator 2%) is displaced to a discharge position and supplies the upper chamber 8 of the jack, the evacuation of the lower chamber 9 being effected through the orifice 29 controlled by the valve 27.

The starting-up of the pump 1 initiates the reverse sequence:

The pressure fluid in conduit 2 re-sets the accumulator 2d, the conduit 3 being exhausted to tank by the valve 30.

The end of the re-setting of the accumulator 20 produces the closure of the valve 30 and results in the movement of valve 27 to cover orifice 29, the rise in pressure of the fluid in conduit 3, the locking of the accumulator by the operating piston 23, and the opening of the controlled valve 21 by the extension of piston 22.

The servo-motor then again resumes the position corresponding to the control signal.

The invention provides that the valves 21 and 27 are housed in a casing 32 which, by rotation of half a turn on itself, permits the direction of return to the extreme position to be reversed, and therefore enables the position of rest to be changed at will.

FIG. 2 represents a further embodiment of the invention in which the same parts are provided with the same reference numerals. The structure is identical to that of FIG. 1, with the exception of the locking of the hydraulic accumulator. In accordance with FIG. 2, the pressure of the fluid in supply conduit 3 holds the accumulator 26* in the set position by acting on a piston 23 which actuates a lever pivoted at a fixed point 41, the said lever being provided with a cam 42. This cam 42 locks a hook 43 pivoted at a fixed point 44; the tip 45 of the hook holds a stud 25 of the rod 25 of the accumulator 20; this hook 43 is provided with a spring 46 which tends to open it. It is the hook 43 which closes the valve 3th.

The operation of the device according to FIG. 2 only differs from that of the device illustrated in FIG. 1 in respect to the locking of the hydraulic accumulator. The stoppage of the pump 1 initiates the following sequence:

Opening of the valve 2.7 which permits the exhaust to tank of the circuit 3.

Closure of the valve 21 and release of the accumulator 2th from its fully charged position by displacement of the piston 23 under the action of its spring 31. The cam 42 of the lever 49 liberates the book 43 which is a) operated by its spring 46 so as to free the stud 25 and permit opening of the valve 30.

The accumulator supplies the upper chamber 8 of the jack, the evacuation of the lower chamber 9 being effected through 29.

The starting-up of the pump ll initiates the sequence in reverse order:

The pressure fluid in conduit 2 resets the accumulator 20, the conduit 3 being exhausted to tank by the valve 30.

At the end of the re-setting operation of the accumulator 20, the stud on the rod 26 of the accumulator comes up against the hook 4-3, causes it to pivot and becomes blocked therein, closing the valve 30.

The closure of the valve causes a rise in pres sure of the fluid in the conduit 3 which results in the locking of the accumulator 20 by the piston 25, the closure of the valve 27 and the opening of the controlled valve 21.

The servo-motor then again resumes the position corresponding to the control signal.

Although the invention has been described with reference to the positioning device according to the abovementioned US. patent application, it will be clear to those skilled in the art that it can be applied just as well to any double-acting servo-jack, the operating pressures of which are regulated by a distributor connected in parallel.

What I claim is:

1. In association with a servo-motor comprising hydraulic supply means under pressure, a double-acting hydraulic jack, two supply conduits supplying respectively the two chambers of said jack, a distributor having two orifices and two conduits each coupling one chamber of the jack to one orifice of said distributor, said distributor including a distributor valve for controlling flow of fluid from said orifices and thereby pressure in said chambers, a device ensuring automatic return to an extreme position of the jack in the event of failure of the hydraulic supply means, said device comprising a hydraulic accumulator, locking means for said accumulator, and means for removing the jack from the control of the distributor valve in the event of failure of the hydraulic supply means, the accumulator comprising a movable element and a spring returning said movable element to a discharged position, the movable element of the accumulator being connected to the supply conduit of the first chamber of the jack of said servo-motor, said locking means comprising a piston subjected to the pressure in the supply conduit of the second chamber of the jack of the servo-motor and holding the movable element of the accumulator in a fully closed position by a mechanical coupling.

2. A device as claimed in claim l, in which said means for removing the servo-motor jack from the control of the distributor valve in case of failure of the hydraulic supply means comprise two valves and a piston, the first valve being provided between the supply conduit of the first chamber of said servo-motor jack and the orifice of the distributor which is connected to said first chamber, the piston being subjected to the supply pressure existing in the second chamber of the servo-motor jack and normally holding open the first valve under the action of said pressure, the second valve being placed in the supply conduit of the second chamber of the servo-motor jack, downstream of the piston operating the first valve and upstream of the conduit going from the second chamber to the first orifice and an orifice for return of fluid to a tank, the second valve being provided with a restoring spring and with an orifice through which passes the supply flow to the second chamber and to the second orifice, said supply putting said valve, against the action of its restoring spring, in a position closing said return orifice to the tank.

3. A device as claimed in claim 2 and further comprising a third valve in the supply conduit of the second chamber of the servo-motor jack, upstream of the piston operating the first valve, a return conduit to the tank, and means for closing said third valve during normal operation.

4. In association with a servo-motor comprising hydraulic supply means under pressure, a double-acting hydraulic jack, two supply conduits respectively supplying the two chambers of said jack, a distributor having two orifices, and two conduits each coupling one chamber of the jack to one orifice of said distributor, said distributor including a distributor valve for controlling flow of fluid from said orifices and thereby pressure in said chambers, a device ensuring an automatic return to an extreme position of the jack in the event of failure of the hydraulic supply means, said device comprising a hydraulic accumulator, locking means for said accumulator, and means for removing the jack from control of the distributor valve in the event of failure of the hydraulic supply means, the accumulator comprising a movable element and a spring returning said movable element to a discharged position, the acumulator being connected to the supply conduit of the first chamber of the servo-motor jack, said locking means comprising a piston subjected to the supply pressure of the second chamber of the servomotor jack, and a cranked lever having one arm actuated by said piston while the other arm holds a stud rigidly fixed to a rod extending from the movable element of the accumulator, said means for removing the servo-motor jack from the control of the distributor valve in the event of failure of the hydraulic supply means comprising two valves and a piston, the first valve being placed between the supply conduit of the first chamber of the servo-motor jack and the orifice of the distributor coupled to said first chamber, said piston being subjected to the supply pressure existing in the second chamber of the servomotor jack and normally holding open the first valve under the action of said pressure, the second valve being placed in the supply conduit of the second chamber of the servo-motor jack, downstream of the piston actuating the first valve and upstream of the conduit going from the second chamber to the second orifice, and an orifice for iIC-lIlLl'Il to tank, the second valve being provided with a restoring spring and an orifice through which passes the supply flow to the second chamber and to the second orifice, aid flow putting said second valve, against the action of its return spring, into a position closing said orifice for return to the tank, said device comprising a third valve, placed between the supply conduit of the second chamber of the servo-motor jack, upstream of the piston actuating the first valve, and a return to the tank, and held closed by the rod of the movable element of the accumulator in the fully charged position of the accumulator.

5. In association with a servo-motor comprising hydraulic supply means under pressure, a double-acting hydraulic jack, two supply conduits respectively supplying the two chambers of said jack, a distributor having two orifices, and two conduits each coupling one chamber of the jack to one orifice of said distributor valve, said distributor including a distributor valve for controlling flow of fluid from said orifices and thereby pressure in said chambers, a device ensuring automatic return to the exrtreme position of the jack in the event of failure of the hydraulic supply means, said device comprising a hydraulic accumulator, locking means for said accumulator, and means for removing the jack from control of the distributor valve in the event of failure of the hydraulic supply means, the accumulator comprising a movable element and a spring returning said movable element to a discharged position, the accumulator being connected to the supply conduit of the first chamber of the servo-motor jack, said locking means comprising a piston subjected to the supply pressure of the second chamber of the servomotor jack, a lever actuated by said piston, and a rotating hook blocked by said lever in a position at which it engages a stud fixed on a rod of the movable member of the accumulator, said means for removing the servo-motor jack from the control of the distributor valve in the event of failure of the hydraulic supply means comprising two valves and a piston, the first valve being placed between the supply conduit of the first chamber of the servo-motor jack and the orifice of the distributor which is coupled to the said first chamber, said piston being subjected to the supply pressure existing in the second chamber of the servo-motor jack and normally holding open the first valve under the action of said pressure, the second valve being placed in the supply conduit of the second chamber of the servo-motor jack, downstream of the piston actuating the first valve and upstream of the conduit going from the second chamber to the first orifice, and an orifice for return to tank, the second valve being provided with a return spring and with an orifice through which passes the supply flow to the second chamber and to the second orifice, said flow putting said second valve, against the action of its return spring, into a position closing said orifice for return to the tank, the device comprising a third valve placed between the supply conduit of the second chamber of the servo-motor jack, upstream of the piston actuating 'the first valve, and a return to the tank, and held closed by said rotating hook in its blocked position.

References Cited by the Examiner UNITED STATES PATENTS 2,733,662 2/56 Hunter 6052 X SAMUEL LEVINE, Primary Examiner.

JULIUS E. WEST, Examiner. 

1. IN ASSOCIATION WITH A SERVO-MOTOR COMPRISING HYDRAULIC SUPPLY MEANS UNDER PRESSURE, A DOUBLE-ACTING HYDRAULIC JACK, TWO SUPPLY CONDUITS SUPPLYING RESPECTIVELY THE TWO CHAMBERS OF SAID JACK, A DISTRIBUTOR HAVING TWO ORIFICES AND TWO CONDUITS EACH COUPLING ONE CHAMBER OF THE JACK TO ONE ORIFICE OF SAID DISTRIBUTOR, SAID DISTRIBUTOR INCLUDING A DISTRIBUTOR VALVE FOR CONTROLLING FLOW OF FLUID FROM SAID ORIFICES AND THEREBY PRESSURE IN SAID CHAMBERS, A DEVICE ENSURING AUTOMATIC RETURN TO AN EXTREME POSITION OF THE JACK IN THE EVENT OF FAILURE OF THE HYDRAULIC SUPPLY MEANS, SAID DEVICE COMPRISING A HYDRAULIC ACCUMULATOR, LOCKING MEANS FOR SAID ACCUMULATOR, AND MEANS FOR REMOVING THE JACK FROM THE CONTROL OF THE DISTRIBUTOR VALVED IN THE EVENT OF FAILURE OF THE HYDRAULIC SUPPLY MEANS, THE ACCUMULATOR COMPRISING A MOVABLE ELEMENT AND A SPRING RETURNING SAID MOVABLE ELEMENT TO A DISCHARGED POSITION, THE MOVABLE ELEMENT OF THE ACCUMULATOR BEING CONNECTED TO THE SUPPLY CONDUIT OF THE FIRST CHAMBER OF THE JACK OF SAID SERVE-MOROR, SAID LOCKING MEANS COMPRISING A PISTON SUBJECTED TO THE PRESSURE IN THE SUPPLY CONDUIT OF THE SECOND CHAMBER OF THE JACK OF THE SERVO-MOTOR AND HOLDING THE MOVABLE ELEMENT OF THE ACCUMULATOR IN A FULLY CLOSED POSITION BY A MECHANICAL COUPLING. 